The invention relates to methods for treatment of neurodegenerative disease and methods for delivery of therapeutic neurotrophins into the mammalian brain.
Neurotrophins play a physiological role in the development and regulation of neurons in mammals. In adults, basal forebrain cholinergic neurons, motor neurons and sensory neurons of the CNS retain responsiveness to neurotrophic factors and can regenerate after loss or damage in their presence. For this reason, neurotrophins are considered to have great promise as drugs for the treatment of neurodegenerative conditions such as Alzheimer""s Disease (AD), Parkinson""s Disease (PD), amyotrophic lateral sclerosis (ALS), peripheral sensory neuropathies and spinal cord injuries.
Direct delivery of neurotrophins through infusion into the neurocompromised brain has been met with limited success and, in one instance, actually worsened the condition being treated (Kordower, et al., Ann. Neurol., 46:419-424, 1999 [symptoms of PD worsened following infusion of glial cell-derived neurotrophic factor]). In contrast, in vivo transduction of CNS cells with a neurotrophin encoding expression vector holds tremendous promise as a more broadly applicable method of treating and preventing neurodegeneration. Ideally, the vector utilized to deliver the neurotrophin will display at least moderate levels of transduction efficiency, while producing minimal toxicity.
The invention provides a lentiviral-based, clinically useful system and protocol for delivery of recombinant neurotrophins into the mammalian brain. The invention is particularly useful in treating neurodegenerative conditions in primates, in whom neurotrophins delivered according to the invention stimulate growth of neurons and recovery of neurological function.
More specifically, the invention consists of methods for intraparenchymal delivery of neurotrophins to defective, diseased or damaged cells in the mammalian brain using a lentiviral expression vector. In one aspect, the invention provides a specific protocol for use in genetically modifying target neurons (xe2x80x9ctarget cellsxe2x80x9d) to produce a therapeutic neurotrophin; e.g., in the substantia nigra or basal forebrain. The genetic modification of target cells is achieved by in vivo transfection of neurons targeted for treatment, or by transfection of cells neighboring these target neurons (neurons or glia), with a recombinant expression vector for expression of the desired neurotrophin in situ.
The location for delivery of individual unit dosages of neurotrophin into the brain is selected for proximity to previously identified defective, diseased or damaged target cells in the brain. To intensify exposure of such target cells to the endogenous growth factors, each delivery site is situated no more than about 500 xcexcm from a targeted cell and no more than about 10 mm from another delivery site. The total number of sites chosen for delivery of each unit dosage of neurotrophin will vary with the size of the region to be treated.
Optimally, for delivery of neurotrophin using the lentiviral expression vector, each unit dosage of neurotrophin will comprise 2.5 to 25 xcexcl of an expression vector composition, wherein the composition includes a viral expression vector in a pharmaceutically acceptable fluid (xe2x80x9cneurotrophic compositionxe2x80x9d) and provides from 1010 up to 1015 NGF expressing viral particles per ml of neurotrophic composition.
This lentiviral based protocol for neurotrophin delivery achieves a high level of transduction efficiency, with minimal toxicity, to produce a therapeutic or preventative effect in the primate brain.